Oil burning heater



Jan. 6, 1942. l w. D. DooLEY I2,268,857

OIL BURNING HEATER Filed May 5, 1939 4 Sheets-Shea*l 1 Jan. 6, 1942. w. D. DooLEY OIL BURNING HEATER Filed May 5, '1959 4 Sheets-Sheet 2 i Jia zag

,U3 YTOFIVEY'S Jan' 6, 1942 -w. D. DooLEY I 2,268,857

. Y OIL BURNING HEATER F'i`led May 5, 19.59 4 Sheets-Sheet 4 Patented Jan. 6, 1942 UNITED OIL BURNING HEATER.

William D. Dooley, Springfield, Ohio Application May 5, 1939, Serial No. 272,028

5 Claims.

The present invention relates to an improvedk oil burning heater which is particularly adapted for use in the curing of tobacco and as a consequence heaters of the type of the present invention are commonlyreferred to as tobacco curing stoves.

In the following description and accompanying drawings the heater is illustrated and described in a preferred embodiment of its use in the curing of tobacco, but it is to loe fully understood that many of the constructional and operative advantages of the present improved oil burnerwould be obtained irrespective of the particular heating use to which the burner is put.

From the foregoing it will .be recognized that the primary object of the inventionis the provsion of an improved oil burning heater for use in the curing of tobacco. Y

Another object of the invention is the provision of a novel and improved method or manner of obtaining and assuring complete and perfect combustion or burning of the fuel oil lin the burner or heater. Y v

A further object of the invention is the provision of an oil burning heater havingnovel `mechanical constructional features such as burner rings of particular ynovel construction aswell as other mechanical features the exact nature and advantage of which will appear in more detail from the following ydescription when read in the light of the accompanying drawings.

Another and `further object of the invention is the provision of a humidifier in combination with the heater. V

A still further object of the inventionis the provision of a single master control for a plurality of the improved burners whereby simplified and proper operation of the burners during the curing of the tobacco is assured.v A

Another and still further object of the invention is the provision of a fuel control Valve that assures the constant delivery of a predetermined amount of fuel to burner irrespective of the temperature to which said fuel is subjected. Y

A still further object of the invention Vis the provision of a novel air delivery and control means for the burner. n

Other specific objects,` improved features of construction and results will appear from the attached drawings when read in the light of the 0f tobacco, a portion of the burner or heater f;

,being broken away and illustrated in verticali section.

Fig. 2 is a bottom plan View of the construction appearing in Fi-g. 1 of the-drawings.

Fig. 3 is a fragmentary vertical sectional view illustrating a modified form of air feeding mechanism for the burner. n K Fig. 4 is a fragmentary top plan 'View of the burner ring illustrated in Figs. 1 and 3 Vof theA drawings. f

Fig. `5 is a vertical sectionalview throughv the improved fuel control valve. y y

Fig. 6 is atop `end view of the fuel control valve. 1 Y Fig. 7 is a horizontal sectional View taken on line 'l-'l of Fig, 5. y l

Fig. 8 is a fragmentary top `plan View of a modified form of burner ring.

Fig. 9 isa fragmentary view in vertical section through the ring appearingin Fig. 8. l

Fig. 10 is a fragmentary top plan view of another` and modified form of burner ring.

Fig. 11 is a fragmentary View in vertical section through the ring appearing in'Fig. 10 of the drawings.

Fig. 1'2 is a fragmentary top plan view of another modied form of burner ring. l

Fig. 13 is a vertical sectional view through the burner ring illustrated in Fig. 12.

Fig. 14 is a fragmentary top plan viewof a further modified form of b urner'ring.

Fig. 15 is a vertical sectional view through the burner ring illustrated in Fig. 14.

Fig. 16 is a fragmentary top plan view of another and further modified'form of burner ring.

Fig. 17 lis a vertical sectional View through the burner ring illustrated in Fig. 16. l f

Fig. 18 is a fragmentary view in kvertical section illustrating the application of a humidifier to the construction illustrated inFig. 1 of the drawings.

In ordinary practice tobacco to yb e cured is placed in a barn or shed and curing stoves are utilized to heat the interior of the building. In many instances four curing stoves are used, one being placed in or adjacent each corner of the building. Y

So far as I am aware it has also been customary in all tobacco curing units heretofore produced and in common use to take air for the stove from the interior of the barn or building. I have` further found that this airA is ordinarily taken either throughthe base o f the stove or through the top of the stove, orthe air is taken in at both the top and bottom of the stove. When the tobacco is rst placed in the barn for curing it has an 80 to 94% moisture content with the result that through the continued application of heat the moisture content of the tobacco is driven off which causes a fog blanket in the building with the result that the air within the building is excessively damp and moisture is deposited around the stove and on the floor of the building. The air for the stove being taken from the interior of the building this heavy water content in the air causes a carbon deposit to form around the stove burner ring and this has been especially true in respect to stoves using lighting or burner wicks. This high moisture content air prevents a complete combustion of all of the fuel oil burned in the stove and a hard carbon or,vin some cases, wax or asphaltum, forms in, on and about these wicks with the result that the flow of oil is retarded or completely stopped.

The base of the stove and the burner ring being hot has been found to cause the oil to boil which causes the oil to vaporize and generate a pressure which has been found to become suiiiciently great as to blow the wick, or fuel distributor as it is sometimes called, out of the top of the stove which scatters hot oil in all directions and has been known to set fire to the barn or building.

I have found that when taking the air for the stove from a point exterior of the barn or building and bringing air to the base of the stove and then distributing it upwardly through the center of the fuel oil well containing the burner ring and by thermostatically controlling the admission of air to the burner the proper amount of air is provided at all times for very eicient combustion and overcomes the objections above referred to. Additionally by thermostatically controlling the air the human element of manually adjusting the air is removed and a consequent better operation of the stove obtained. I have further found that in respect to down-draft stoves as now used the xed inlet or orifice of the downdraft tube which might maintain an efficient combustion at one predetermined setting from a predetermined oil delivery will not operate to provide maximum efficiency of combustion when a greater or lesser oil feed to the burner is obtained. In other words there is approximately only one point or one condition in the entire range of operation of stoves as now used where they can or will perform at anywhere near the peak or maximum efficiency.

In the curing of `tobacco properly it is necessary to provide a unit which will uniformly cure the' tobacco and the unit as a consequence must be capable of operating to provide a positive constant uniform temperature, regardless of outside weather conditions, during the coloring stage. After the tobacco leaves have become uniformly yellow the neXt stage in the curingis that of setting the color at which time the temperature within the barn must be increased. It is during this stage that units as now made and in use are decient because it is during this stage that the hereinbefore referred to high humidity condition within the barn exists and causes improper combustion which makes it diicult if not impossible to obtain the steady correct rise in heat which is necessary. The present invention makes provision for the necessary accurate control of heat delivery.

During all stages of the curing process Ait is highly essential for the best curing of tobacco 4to accurately control the heat within the barn which means that there must be an accurate control of the burner or heater. Such control is provided by the present invention.

After the tobacco has been cured and is ready to cool it must be brought in order or case for handling. In the past this step of the process has been accomplished by opening the doors and ventilators of the barn and allowing the natural moisture of the air to bring the tobacco into condition to be handled. This is called natural casing and requires one to several days depending upon the moisture condition of the air. The present invention provides a uniform condition for bringing tobacco into condition for handling in that means is provided for adding moisture to the air within the barn.

Additionally the construction is such that the air is preheated prior to its delivery to the burner with the result that the burner operates as though it were used in combination with a blower. This is due to the fact that the arrangement is such that combustion really takes place in a partial vacuum. This partial vacuum is brought about by reason of the fact that the thermostatically operated damper is always behind the ame or heat, by which is meant that the setting of the damper is such that it is stingy with the admission of air in respect to the stack draft with the result that the velocity of air is stepped up and acts as a blower. In other words, as the air is preheated its volume increases with a resultant increase of velocity of air in the preheating manifold. It is to be noted that the stack outlet is larger than the air inlet with the result that the damper setting can be such as to cause the partial vacuum referred to.

The outlet from the drum to the flue is so positioned with respect to the top of the drum as to provide a space above the flue outlet within which the hot products of combustion will collect and prevent the draft from causing the flame to flutter or blow out.

Another advantageous and desirable feature is that of the adjustable baille above the burner drum which enables the operator to direct the heat to different portions of the barn or chamber in which the tobacco is being cured.

Astill further improved result is found to reside in the fact that the hot oil acts as a solvent to constantly clean the grooves in the burner rings.

In addition to the foregoing other specific objects, advantages and improvements of the invention will be apparent to those skilled in the art from the following description when read in the light of the accompanying drawings, and among these will appear the ease and low cost of operation of the improved burner.

Referring now to the drawings and particularly Fig. 1 thereof in which one embodiment of the invention is illustrated, l designas the outer wall of a tobacco curing barn or building adjacent one corner thereof while the present improved oil burning heater or curing stove is designated as an entirety by A. It is to be understood that in ordinary practice a curing stove will be positioned adjacent each of the four corners of the barn, room or chamber within which the curing operation is carried on.

The stove or burner is preferably, although not necessarily, cylindrical in form and comprises a base 2 which is supported above the floor 3 of the building by suitable legs 4 the upper ends of which are threadedly and adjustably connected as at 5 with the base 2 of the burner. Once the height of the burner is properly adjusted it is locked in this position by suitable'lock nuts 6. Itlwill be obvious that these legs provide a convenient means by which the height of the stove as well as the level of the base can be conveniently and quickly adjusted. A

The stove or burner drum body is designated at 1 and is provided with a suitable top 8 having a central opening which is normally closed by a removable lid or closure plate 9. 5

The stove base is provided with an air inlet passageway I to which air is delivered by an air inlet conduit II which is bolted or otherwise suitably secured to the under side of the stove base as at I2. An extension conduit IIa is connected to the air inlet pipe and has 'its inlet end positioned at some point exterior of the building so that the air delivered to the burner is brought from a point outside of the room within which the heater is operating.

The stove is provided with a conventional outlet ue or stack I3 which s connected to the burner drum as at |4 at a point below the top or cover 8 thereof. This stack extends upwardly within the barn and passes out ordinarily though not necessarily through the roof thereof. It has been found that many res have beenr caused by not providing proper support for the outlet flue of the stove and as this flue becomes very hot it will be apparent thatr should it fall it could readily cause the barn to be set are. To guard against this contingency the elbow portion I5 of the flue pipe is supported by a vertically extending or disposed arm or rod I6 the lower end I1 of which is in the form of a spike which extends into the floor of the building while its upper end is forked as at I8 to receive the pipe elbow. A semi-circular clamping member I9 extends around the upper half of the pipe and is secured to the forked end of the support by suitable bolts or the like.

Similar, though shorter, members 2| are provided for securing and bracing the vertical portion of the flue I5. Only one such member is illustrated but it is tobe understood that the number utilized would be governed by the length of the ue pipe. i

Still having reference to Fig, 1 of the drawings, a fuel tank is designated at B and may be placed where ever desired, preferably exterior of the barn, to provide a gravity type of fuel feed. A

control board C is conveniently positioned for operation and carries the master fuel control valve designated as an entirety by D. `Fuel is delivered from the tank B to the control valve by a pipe 24 while a pipe 25 leads from the control valve to a suitable fitting 26 which has a plurality of outlets the number of which will be controlled by the number ofburners or stoves in the barn. In the present instance only two outlets are illustrated and accordingly there are two pipes 21 and 21a leading from the fitting. In each of these pipes there is vdisposed a Vfilter E.

The fuel delivery pipes 21 and 21a in each instance lead to the bottom plate 2 of a burner or stove and has communication with the bottom tures.

f out t'provide an overflow chamber '30 into which excess fuel oil will ilow from the burner trough and "be led away to discharge by a suitable overflow conduit or pipe 2| if for any reason the fuel as delivered to the burner ring trough is not consumed by reason of its failing to be ignited and burned.

A conical air and heat distribution plate or baille is designated as an entirety at G and is supported in spaced relation above the burner ring by suitable legs 32. On its upper face the baille is provided with a collar 33 which telescopically receives the lower end of the preheating airmanifold pipe 34 which extends vertically for a considerable distance within the stove drum and is then provided with a cross head 35 to which is connected a second and downwardly extending vertically disposed leg 34a the lower end'of which is in telescopic connection with the air inlet I0 of the stove base. `The preheating manifold is held or braced againstk accidental displacement by a suitable brace I 50.

The thickened portion of the burner base adjacent the overflow chamber or reservoir 30 is provided with a circular groove I5I in which the fuel oil is caught prior to running downwardly into the sump or overflow chamber 30. Here the oil is preheated or gasified when the burner or stove is first put into operation or first started.

The air delivered to the burner through the preheating manifold is under the control of a thermostatically operated damper. This damper l is in the air inlet pipe and is designated at |52 and carriesA a weight |53 which tends normally to hold it in a closed position. At the under .side of the stove base 2 and preferably within a protective housing or box |54 there is positioned a bimetal thermostatic element I 55 the free end of which engages the end |56 of a bell crank lever which through suitable linkage and a connecting rod |51. is-operatively connected to the damper, all of which is readily apparent byvreference to Figure 1 of the drawings. This thermostat is responsive to the heat generated by the burner and is so set as to operate the damper in a manner to somewhat starve the burner for air. the damper so that the amount of air permitted to pass it will not equal the amount or volume of air being discharged through the larger outlet flue `or Vstack I5, with the result that the burner vwill operate in a partial vacuum. The preheating of the air in the preheating manifold will `increase the volume of air therein and step up the velocity of air with the result that the burner will operate as though a blower were being used .with it.

Afuel'valve has once been set to deliver a predetermined amount 'of fuel to the burner that this accurate set delivery be maintained. I have made provision for accomplishing this result through the provision of the hereinbefore referred to master control valve D.

The fuel which is delivered to the burner will of necessity be subjected to varying v.tempera- The fuel tank B will be exteriorof the curing rbarn or buildinghin which the heaters are operating and the fuel delivery pipe 24 will also be exterior of that building. It is possible that the control board C will also'b exterior of That is to say, the thermostat will operate the barn and if this be true additional fuel piping as well as the master control valve itself will be exterior of the heated barn or building. Whatever the arrangement the fuel oil will 'unquestionably be subjected to varying temperatures and it is a proven and recognized fact that the viscosity of fuel oil will vary with temperature changes. It follows therefore that when a valve is set to pass a predetermined amount Aof fuel over a predetermined period that the amount of fuel passing the valve would not remain constant when the viscosity of the fuel is changing due to temperature changes.

As an instance and example of the preceding remarks let it be assumed that a valve was set to pass 100 drops of fuel oil per minute when the fuel oil is subjected to a temperature of 80 F. Should the temperature during the day or night fall to 60 F. the viscosity of the fuel would increase with the result that instead of the valve passing 100 drops per minute only approximately 60 drops would be passing through the valve orifice. My master valve which I will now describe will assure that 100 drops per minute will pass through the valve irrespective of any change in the viscosity of the fuel after the valve has been set.

Having reference to Figs. 5 to 7 inclusive of the drawings the valve comprises a casting having an upper portion 36 forming a fuel receiving chamber 31 closed at its upper end by a removable cover 38 and at the lower end by an intermediate stem-like portion 39 having a passageway therethrough. Beyond the lower end of the stem portion the casting is formed with an arm portion 40 terminating in a base 4l having a passageway therethrough. Fuel from the tank B is brought to the valve chamber 31 by the aforementioned fuel pipe 24 and passes from this chamber under the head 42 of a valve the stem 43 of which reciprocat-es and is guided in the opening in thestem or sleeve portion 39 of the housing. The head of the valve 42 cooperates with a valve seat 44 at the upper end of the sleeve while at its lower end the sleeve is provided with a removable plug 45 having a fuel passageway 46 therein. The outlet end 46 of the plug passageway is within a glass tube or conduit 41 which provides for visual determination of the fuel delivery to the several burners or stoves.

The lower end of the glass tube 41 is seated withinA the housing base 4I and communicates with the passageway 48 thereof. A continuation of the fuel pipe 24 is connected to the base 4I and carries the fuel which passes the valve head 42 to the aforementioned fitting 26 from which it is led to the several burners or stoves.

A coil spring 49 positioned under the lower end of the valve stem 43 tends normally to hold the valve in an open position. A coil spring 56 within the fuel chamber 31 and engaging the upper face `of the valve head 42 exerts a force and opposition to the spring 49 but the spring 49 is stronger than the spring 5i). The upper end of the spring 50 engages the lower end of a plunger 5I which is reciprocable within a boss 52 formed as a part of the cover 38. The upper end 53 of this plunger extends outwardly :beyond the boss and cover and is held against escapement and also reciprocable by an eccentric cam 54 which is rotatable with a horizontally disposed shaft 55 the outer end of which carries a setting handle or knob 56 which provides manual means for rotating the shaft and cam. The

valve cover 31 is provided with two upwardly extending arms or bracket-like parts 51 and 58 which receive between them the shaft 55 and serve as a supporting bearing therefor. A screw 59 is provided for tightening the bracket parts in proper operative supporting relationship to the shaft. O-n their outer faces the brackets or arms 51 and 58 carry an indicating dial 60 upon the face of which will be printed the proper graduations to indicate the setting of the valve 42. The setting handle or knob 56 is provided with -a hub portion 6I formed to have a pointer portion 62 which is movable over the face of the dial 60.

H designates as an entirety a bi-metallic thermostat one end of which is secured as at 63 to a boss 64 formed as a part of the bottom of the chamber 31. This flat thermostatic member has its opposite end cut out as at 65 to provide armlike portions 66 and 61 disposed in separated parallel relationship. The valve head 42 is provided with an upwardly extending reduced portion 68 which is disposed in the cut-out portion 65 between the aforesaid arms or fingers 66 and 61.V The reduced portion 68 of the valve at its upper end terminates in an enlarged disc-like portion 69 which is disposed immediately above the fingers or arms 66 and 61 of the thermostat. Thus it will be seen that as the thermostat ilexes in accordance with temperature variations it will tend to open or close the valve.

The thermostat H will be submerged in the fuel within the fuel chamber 31 and will of course therefore be subjected to the temperature of the fuel oil and will respond in its operation to the temperature changes to which the fuel oil is subjected.

In operation let us assume that the setting handle 53 has been positioned so that the valve 42 will pass 100 drops of fuel per minute when said fuel is at F. When night comes on and the viscosity of the fuel decreases by reason of the temperature having dropped to 60 F. the thermostat H will respond by having a tendency to assume a more horizontal position and through this endeavor willr-aise the valve against the tension of the coil spring 50 and will raise it the exact amount needed to maintain past the valve the passage of drops of fuel oil per minute.

From the description thus far given it will be apparent that I have provided a means for manually adjusting or setting a valve to pass a predetermined amount of fuel under a predetermined temperature condition and that thereafter the valve will be automatic in maintaining the passage of fuel in the amount set or predeterminedly selected and will pass this amount irrespective of the change in temperature and the change of the viscosity of the fuel. It will be further seen that by a single master valve a predetermined flame can be maintained in any one of a plurality of heaters or stoves.

It is essential to the proper operation of the burner under the conditions to which it will be subjected that the air for the maintenance of combustion will betaken from a point exterior of the building or barn as has been mentioned. It is also essential that the amount of air delivered to the burner beproportioned in accord with the amount of fuel being consumed by the burner, which means of course that the air should be predetermined in accordance with the heat being delivered by the burner.

Theproper proportioning and delivering of air is taken care of by the thermostatically operated damper heretofore referred t0.

For the purpose of providing means' to direct heat to different portions or areas'of the barn and to provide means to prevent overheating at a point directly above the stove I provide a baffle K which is circular in form and slightly larger than the curing stove land supported inspaced relationship thereabove by a `centrally disposed arm 12 the lower end of which has universal oonnection as at 13 with the removable lid or closure 9. The baille is provided ywith a handle 14 by which it can be conveniently manipulated to set it at any desired angle for deflecting or directing heat to the desired larea of the barn.

It will be apparent that the baifle Kis bodily removable as a unit with the closure plate or lid 9. To provide means for humidifying ther air within the curing barn or chamber at thattirne when this is necessary irythe process o f properly curing the tobacco I have provided av cone shaped water reservoir designated as an entirety at R which is placed in the opening in the top 8 of the stove when the baille Kand lid 9 are removed therefrom as is clearly illustrated inV Fig.. 18 of the drawings. This reservoir has suitable brackets or legs 15 attached to it and the lower ends of these legs engage the top 8 of thel stove and support the reservoir in the manner illustrated in Fig. 18 of the drawings wherein it will be seen that the lower end or lapex of the reservoir is within the burner chamber of the stove with the result that the water carried by the reservoir will be heated and in that manner humidify the air within the barn or curing chamber. Y

In Fig. 3 of the drawings a modied form o the invention is illustrated. The construction here illustrated is more costly of manufacture than is the construction illustrated in Fig. 1 of the drawings. The burner bottom or base |58 is slightly modied in `its construction in that the burner ring trough is not formed asa part; of the burner base but is a separate casting designated as an entirety at S which lis secured to the burner base as at |59 and includes the burner ring trough |65 and the overow well or sump IBI, all of which is disposed within an opening |62 centrally formed in the burner ybase and provided with an upwardly extending flange or collar |63 which is arranged in spaced relationship to the burner ring trough to provide an annular air admission passageway |84.V

There is the same fuel delivery pipe 21 and fuel overow pipe 3| as well as the same baffle G, air inlet opening I and preheating manifold made up of the legs 34 and 34a.

The air admission conduit la in this instance communicates with a large housing designated as an entirety by T which is suitably' bolted or secured las at |65 to the stove` base |58. This casting T forms a continuation of the air conduit Ha and communicates not only with the preheating manifold through the air inlet opening I0 in the stove base but also delivers air past the burner ring F and burner trough |69 through The, particular? and specific constructions `of the several .burner rings is important in assuring complete "and perfect" combustion.' 'Several alo the annular passageway |64 so that air is also y .forms of yburner rings are .illustrated...in Vthe drawings andwillnow be described.

In'Figures 1, 3, and 4;.of the drawings the burner ring is designated as F. and has been before referred to. 'Having reference to4 Figure 1 of the drawings wesee'that thefuel receiving trough 29.0f the .base 2 has a flat bottom'16 and that it has4 an outer substantially vertical'y wall 11 while its inner wall 18 extends inwardly and upwardly. `This makesthe fuel trough.: or burner ring receivingtrough widerat its upper end than at its lower end.

The burner ring F "s metallic and consti tuted of a single piece. It has a cross sectional configuration similar to the cross sectional coniiguration of the burner trough. The tapered wall 19 of the ring yabuts the tapered wall of the trough `while the outer vertcal'wall of .thering is provided ,with a plurality of vertically extending grooves or channels arranged in spaced relationship throughout the periphery of this wall of the ring. The bottom 8| of the ring rests upon the bottom of the trough and additionally the bottom of thering is provided with a cir.- cumferential cut-out portionforming a groove 82 so that when the heater is in operation and the base V2 thereof and the burner ring F are hot vapor can rise in the channelways 80 to .be burned at the top ofV the ring. The top` 83 of the ring extends above theiiat top 84 of the ver.- tical sidewall of the burner trough and is substantially flush withthe rtop 85 of the inclined wall' of the burner trough. The ring is providedfwith oppositely disposed upwardlyl extending lugs 86 each of them having therein an opening 81 so that by the use of suitable'tools the burner ring can be lifted outwardly through the upper end or cover 8 of the burner drum 1 when it is desired to clean the ring or replace it with a different ring. Theburnerr ring F is designed particularly for maintaining an extra low sustained temperature under Ywhich conditions` a small amount of oil will be burned over long periods of time. Combustion willtake place only at that edge of the ring which is provided with grooves B9. v v a In Figs. 8 and 9.0i the drawings a modified form of burner ring is illustrated. Thisparticular burner ring is designated as an entirety by L and is designed for quick generation and to combust amaximum of 3 gallons of fuel oil perhour. y.,

This particular ring rests only in the -upper end of the combinedgfuel and burner ring trough 29 as is apparent in Fig. 9 of the drawings. At its upper edge the ring is-provided with a plurality of fuel grooves or passageways 88. The portions 89 of the ring between the grooves engage the vertical wall 11 of the burner trough and the opposite or inner edge 98 of the ring is tapered to engage the slanting wall 18'ofthe burner trough. This engagement between the parts support the ring in the upper end of the trough wall abovev the bottom thereof. On its upper face the ring is provided with a plurality of transversely extending Vgrooves 9|. There is one transverse groove for each vertical groove 88 and at theirk outer ends the grooves 9| merge into the said grooves 88. The horizontal grooves 9| extend entirely across the upper face of the burner ring. In operationthe oil is fed into the fuel trough 29 until it passes up through the vertical grooves 88 into the horizontal grooves 9| to obtain what I call surface vaporization.

The number of transverse grooves is such as to provide an excess to those actually needed to burn the stated amount of fuel with the result that a large proportion of the grooves could become clogged and the burnerwould still operate to burn the full amount of fuel delivered to the burner trough and in this way prevent any possibility of the generation of a pressure which would be likely to cause an explosion.

This ring as well as the first described ring and the rings hereinafter to be described are made of cast iron which of course becomes hot and forces the oil up through the grooves at the outer edges of the rings in a semi-vaporized condition.

Those burner rings, such as ring L, which are provided with transversely extending grooves make it exceedingly easy to ignite the fuel oil by the application of a match and thereby obviate the necessity of the use of a so-called lighting Wick.

In respect to all the burner rings it has been found that by feeding the oil up the outside 3 edges thereof there is a solvent action of the oil which tends to liquefy or solvenize any wax or asphaltum which is present in the fuel oil and which would have a tendency to make the burner ring stick or adhere in the burner ring trough. In burners with which I am familiar this Wax or asphaltum has been known to become so hard as to require the use of a cold chisel whenit has been found desirable or necessary to remove the burner rings. This objection is overcome by my improved burner ring constructions.

In Figs. 10 and 1l a still further modified form of burner ring is designated as an entirety by M. This ring is designed for the same purposes as the hereinbefore described burner ring L and differs therefrom only in being provided at its bottom with a narrow circumferential ring portion 92 which engages the bottom of the trough 29 and serves to support the burner ring therein. In this instance the outer edge portions 89 of the ring are slightly spaced from the vertical wall of the trough as indicated at 93. The ring has the same vertical grooves 88 and horizontal grooves 9|.

The burner ring N illustrated in Figs. 14 and 15 of the drawings presents a further modification of the invention. This ring has the vertical grooves 88 and the transverse grooves 9| and the outer ring portions 89 are spaced as at 94 from the vertical wall of the trough. This y ring throughout its depth has its inner wall 95 engaging the inner tapered wall 18 of the burner trough. Below the grooves 88 however the outer wall is cut backwardly and downwardly as indicated at 9B to provide a comparatively thin supporting portion 91 which engages the bottom of the trough. The oil within the trough in this instance is all at the left side of the supporting portion 91 of the ring. This particular ring is designed to burn for long periods at low temperatures and still keep generated.

The burner ring O illustrated in Figs. 10 and 11 of the drawings is of very light construction and has been especially designed to burn kerosene very efficiently. Some operators have found it desirable to use kerosene as a fuel oil. This ring, like the rings in Figs. 8 and 9 of the drawings, is supported in the upper end of the trough 29 and is provided with a central feed which is in the form of a plurality of holes or passageways 98 arranged in spaced relationship throughout the perimeter of the ring and central thereof in respect to its width. There is a transverse groove 99 in the upper face of the ring communicating with each vertical passageway 98.

The burner ring P illustrated in Figs. 16 and 17 of the drawings is in reality a reversal of the structures appearing in some of the previously described burner rings in that this ring is provided With a series of vertically extending spaced oil grooves |00 in the inner slanting wall |0| of the ring whereas in the other structures these grooves have been in the outer walls of the rings. This ring completely fills the trough 29 and has in its bottom a circumferential groove |02 which communicates with all the aforementioned vertical oil passageways |0I. 'Ihis ring on its upper face is provided with transversely extending grooves |83 one of which is provided for and has communication with each of the vertical grooves IDI. 'Ihis ring is particularly adapted to burn low viscosity fuel.

All the burner rings are provided with perforated ears 86 to facilitate their removal from the burner ring troughs and out of the burner drum through the lidded opening 9 thereof.

The bottom 2 of the burner or stove is all cast in one piece which makes for an extremely cheap stove construction and enables the present burner to be sold at an unusually low price.

The master control valve makes it possible to simultaneously regulate all of the curing stoves in the barn at the same time which is of course highly desirable. On the other hand if for any reason it should be desirable to provide indi vidual regulation for each of the stoves in a curing unit this could be easily done by merely providing a master control valve in the fuel delivery line to each of the stoves. An alternate arrangement would be the use of two master control valves so that simultaneous adjustment could be had for two of the stoves on one side of the barn and simultaneous adjustment would be provided for the remaining two stoves at the other side of the barn. The main feature of the control is that irrespective of the number of master control valves provided they would in each instance definitely assure the operation of the stove at the setting of the valve irrespective of any change in the viscosity of the fuel due to temperature changes.

The advantages and novel features of construction having been pointed out in the foregoing description and being apparent to anyone skilled in this art, it Will be understood that the invention is limited only by the scope of the hereinafter appended claims.

I claim:

1. An improved oil burning tobacco curing stove for use in a tobacco barn or shed, comprising a heating drum closed against communication with said shed or barn, an air inlet conduit having an inlet end exterior of said shed or barn and communicating with said drum, an outlet flue from said drum to a point exterior of the shed or barn of a size capable of discharging a greater volume of air than can be admitted to the drum by said air inlet conduit, an oil burner in said drum including an oil ring Within which oil is adapted to be vaporized, a preheating manifold within said drum through which said air must pass for delivery to said oil burner, an air controlling valve in said air conduit, means tending normally to close said valve, thermo means responsive to the heat generated by said burner for opening said valve, and said thermo responsive means acting to increase the opening of said valve as the heat generated by said burner is increased but acting at all times to permit only the delivery to said burner of less air than can be consumed thereby and discharged through said outlet flue, whereby said burner is caused to operate within said drum in a partial vacuum.

2. An improved tobacco curing stove, comprising a heating drum having a liquid fuel burner in the lower end thereof including an oil ring within which oil is adapted to be vaporized, an outlet flue for said drum, an air inlet in the lower end of said drum and capable of conveying to said drum a lesser Volume of air than can be discharged from said drum through said outlet flue, an air preheater within said drum comprising a stand pipe conduit having a pair of vertically disposed spaced legs, one of Said legs connected to and receiving air from said air inlet and the other of said legs extending downwardly and concentrically over said oil ring and terminating in an outlet end at a point above the ring,v

the outlet end of said leg being of lesser size than the size of said ring, a baille carried by the outlet end of said leg and extending upwardly and outwardly over said ring to direct the admitted preheated air laterally over said ring a valve for discharged through said outlet flue, whereby said ing a heating drum having an opening in its bottom, a liquid fuel burner loosely supported in said opening to permit the inward passage of air through said opening past said burner, a second air inlet passage in said drum bottom, an air inlet conduit having an inlet end exterior of the room within which said stove is positioned and communicating with both of said air inlets in the bottom of said drum, an air preheater within said drum communicating with said second air passageway in the bottom thereof and having a vertically disposed leg concentrically arranged above said burner and-having an outlet end terminating at a point above the burner, and an outlet flue for said heating drum.

4. A construction such as dened in claim 3, wherein said air inlet passageways into said drum have a combined capacity less than the outlet capacity of said outlet ilue, whereby said burner is partly starved for secondary air and operates in said drum in a partial vacuum.

5. An improved tobacco curing stove, comprising a heating drum having an oil burner therein, an air inlet conduit communicating with said drum, an outlet flue from said drum having a discharge capacity of a greater volume than the admission capacity of said air inletv conduit, a normally closed Valve in said air inlet conduit for controlling the passage of air therethrough, thermo means responsive to the heat generated by said burner for opening said valve, and said thermo responsive means acting to increase the Vopening of said valve as the heat generated by said burner is increased but acting at all times to permit only the delivery yto said burner of less secondary air than can be consumed thereby and discharged through said outlet ue, whereby said burner is caused to operate Within said drum in a partial Vacuum.

WILLIAM D. DOOLEY. 

